channel_pre_listener
pre[SSH_CHANNEL_PORT_LISTENER] = &channel_pre_listener;
pre[SSH_CHANNEL_RPORT_LISTENER] = &channel_pre_listener;
pre[SSH_CHANNEL_UNIX_LISTENER] = &channel_pre_listener;
pre[SSH_CHANNEL_RUNIX_LISTENER] = &channel_pre_listener;
pre[SSH_CHANNEL_X11_LISTENER] = &channel_pre_listener;
pre[SSH_CHANNEL_AUTH_SOCKET] = &channel_pre_listener;
pre[SSH_CHANNEL_MUX_LISTENER] = &channel_pre_listener;